The Solar Monkey Adventurer is a 3 Watt solar panel combined with a 2500mAh lithium polymer battery in a ruggedised foldable case. It weighs exactly 9oz, not including case and cables. The manufacturers website is

It comes with a well-made nylon case, charging cable, an assortment of charging tips, and a carabiner. Overall, it feels like a well made, high quality device.

My interest in this charger was to see if it would keep my iPhone and my Sony Rx100 II camera charged up for a 220-mile hike of the John Muir Trail in California. This would be a two or three week trip with no opportunity to recharge batteries other than by solar panel. I was looking for something light, and with a built in battery. You cannot charge an iPhone properly with a solar panel that does not have its own battery, because every time the solar panel output drops due to a passing shadow, the iPhone decides to have a fainting fit, stops charging and goes into sulk mode for a random length of time that might be hours. It just doesn't work unless you can guarantee uninterrupted sunshine. The SolarMonkey Adventurer seemed to be one of the lightest panels around that had a battery and a decent capacity solar panel, so I gave it a go.

Here's how it looks with its blue case...

Here it is on its own, in the closed position...

And here is the unit folded open...

And here it is charging an iPhone with the included dog-bone cable...

Field Results:

I used the Solar Monkey for 13 days hiking the John Muir Trail. I had it strapped to the top of my backpack, facing straight up. I found that it could charge fully over the course of one day. Once charged, it could then fully charge an iPhone 4S and a Sony RX100 battery. That was more capability than I really needed, because the iPhone would last for three days on a single charge, and the Sony RX100 even longer. However, it was good to know that I didn't have to worry about using the iPhone all day long. I had a few rain showers, and that was not a problem.

Alternatives:

A rechargeable battery pack might be a good alternative for short trips. Figure that the Solar Monkey can provide about 2,000mAH per day. If you are out for five days, you are getting 10,000mAh. You could get that much energy out of a battery pack that weighs the same as the Solar Monkey, and you wouldn't have to worry about putting it in the sun all day. But if your trip goes beyond 5 days, then the battery solution is going to be heavier than the Solar Monkey, or you are going to need somewhere to plug in a charger. On the john Muir Trail, the Solar Monkey makes sense. you would be hiking for around two weeks, and there is only one opportunity in the middle to charge batteries, but you would be waiting all day to get that done.

After a couple of years, the Solar Monkey case started to deteriorate and become permanently "sticky". I wasn't too bothered about that, since I had enjoyed some good use out of it, but rather than just chuck it in the trash I decided to take it apart in the interests of science and see what was inside.

So the two sides are joined together by a rather fancy hinge with brass sleeve inserts. That is a neat touch. Inside the thicker side is a 2500mAh battery...

2500mAh is not a huge amount of charge, but in fairness, it is exactly what is claimed on the Solar Monkey web site and on the label, so there is truth in advertising after all. A lot of manufacturers try to fool you with an mAh figure without telling you that it's for the internal 3.7 battery, not what can be delivered at 5V on the USB port. Solar Monkey gives the capacity in Watt Hours (Wh), which is not dependent on whether you are talking about the 3.7V internal battery or the 5V output. So props to Solar Monkey for being about the only honest manufacturer out there.

Also inside the thicker panel is a small circuit board that converts the 3.7V from the battery to 5V at the USB port. It also takes 5V in from the charging port and/or the solar panels and converts it down to 3.7V to charge the battery. I don't know if it can deliver 5V and charge at the same time, but I suspect it can.

I looked at the Solar Monkey website to see how much a new one would cost, and noticed that they have now upgraded the battery to 3000mAh, which is a decent upgrade. Overall I would say the Solar Monkey is a good product, although the sticky rubber effect needs to be sorted out. If you keep it in the sun, you should be able to keep the internal battery topped up every day and keep a phone charged.